1. Field of the Invention
The present invention relates to a safety brake for use in immobilizing the chute of a cement truck from lateral rotatation relative to the cement truck chassis.
2. Description of the Prior Art
In the construction of concrete foundations, roadways, sidewalks, bridges, and numerous other civil engineering construction projects, premixed concrete is transported in slurry form to a job site in a cement truck. A cement truck includes a very large mixing drum which rotates upon the cement truck chassis to continuously mix the aggregate and cement as the premixed concrete slurry is transported to the construction site. The rear extremity of the rotatable mixing drum of a cement truck tapers to form an opening from which the uncured concrete is poured at the job site. A conventional cement truck includes a pneumatically or hydraulically operated system for tilting the drum rearwardly in order to pour the premixed, uncured concrete from the mixing drum. The flowing concrete slurry is guided by a hopper, which is secured relative to the cement truck chassis, into a discharge chute, likewise connected to the cement truck chassis. The upper extremity of the discharge chute is positioned to receive concrete mix from the discharge hopper.
To minimize the time and labor involved in pouring concrete, the chute is provided with a system of extensions to direct flowing concrete mix from the discharge hopper directly into the forms in which the concrete is to be cured. Oftentimes the desired direction of discharge is laterally to one side or the other of a cement truck.
In order to have the flexibility to direct flowing concrete mix in various directions to the rear and to either side of the body of the cement truck, the chute is pivotally mounted relative to the chassis so that it can be rotated about both horizontal and vertical axes. Rotation about the vertical axis swings the chute from side to side in order to laterally discharge the concrete mix to a desired location. Rotation of the chute about a horizontal axis adjusts the angle of inclination of the chute. The desired angle of inclination will vary with the distance from the cement truck at which the concrete mix is to be deposited.
In conventional cement trucks, adjustment of the angle of inclination and rotation of the chute about a horizontal axis is controlled by a pneumatic ram. Such a ram includes a piston movable within a pneumatic cylinder. The ram is connected to the chute at some distance from the axis of rotation of the chute relative to the cement truck chassis. Lateral positioning of the chute to rotate about a vertical axis is normally performed manually. That is, the chute is manually pushed laterally by hand in rotation about a vertical axis to a desired orientation relative to the longitudinal axis of the cement truck chassis. The end of the ram remote from the chute is connected to a vertical ram pivot axle which is rotatably mounted within a sleeve or collar that is rigidly secured to the cement truck chassis.
In conventional practice, the ram pivot axle is equipped with a hydraulic or pneumatic brake, which is provided in order to prevent the ram pivot axle, the ram, and the chute from rotating about a vertical axis once the chute has been moved laterally to the desired position. Some of the more widely used cement truck chute brakes are marketed under the names Challenge, Rex and McNealis.
Very significant problems exist in the operation and maintenance of conventional cement truck chute brakes. Conventional brakes which are commercially available tend to rapidly become clogged with pieces of aggregate. The cork brake pads employed rapidly deteriorate due to the abrasion caused by grinding the chunks of concrete therebetween. After use for only a short time the conventional brakes, which are presently commercially available to prevent the ram pivot axle from rotating, become virtually ineffective.
Conventional cement chute safety brakes become clogged with layers of grout and cement and frequently bind up even when deactuated. When this occurs the cement chute can be rotated from side to side only by first dislodging the grout and concrete from the safety brake. This is normally done by beating and pounding on the layers of cement and grout with a hammer or other heavy implement. While this technique for removal of accummulated matter obstructing movement of the cement chute is an expeditious way to free up the brake, very typically this technique results in severe damage to the brake and prevents proper operation of the brake thereafter.